Manufacture of artificial filaments



@Ct. 17, 1933. w soN 1,930,803

MANUFACTURE OF ARTIFICIAL FILAMENTS Filed Oct. 22, 1928 III i PatentedOct. 17, 1933 William Harrison, Kilmacolm, Scotland Application October22, 1928, .Serial l\To. 314,324,

and in Great Britain November 1, 1927 2 Claims. (01; 18-54) It is knownto spin viscose by what is known as the stretch spinning processaccording to which the formed threads are drawn away from the jetorifices at a greater velocity than that 5 at which the viscose solutionissues from the orifices.

It is also known to produce artificial silk of higher strength thanusual, that is to say, higher strength than is obtained by a simpleprocess of stretching, e. g., 2 grams per denier, by the use of aswelling agent for cellulose such as strong acids of hydrionconcentration greater than that of a 45% solution of sulphuric acid,zinc chloride and calcium thiocyanate, the thread being stretched whilein a plastic state occasioned by the use of a swelling agent immediatelyafter (one bath process) or some time after (two bath process) thesetting or -decomposition operation during-which cellulose is formedfrom the viscose. In other words, the cellulose formed in the settingprocess is caused to swell by the application of a cellulose swellingagent; or agents and while thus swollen the threads are stretchedconsiderably and the swelling agent removedu The object of thisinvention to produce strong threads from viscose without the use of suchswelling agents and without the use of exceptionally strong acids, thatis to say, without usingacids of hydrion concentration corresponding tothat of a 45% solution of. sulphuric acid,the acids if used beingadvantageously of considerably lower concentration.

I'attain my object by the application of tension and extension in amanner'and under con-' ditions hereinafter described which have nothitherto been applied in the spinning of viscose silk.

' According to one embodiment of my invention I use as coagulantsfor theviscose, preferably viscose made from unaged or only partially agedalkali cellulose, baths containing strong or mineral acids of hydrionconcentration less than that of a 7% solution of sulphuric acid, down toeven 0.5% or less, preferably in the presence of neutral salts, andthereby effect coagulation of the viscose and slow decomposition intocellu lose. With such a coagulating bath the viscose after coagulationexists for 'a short time in an evanescent oran active plastic state,that is to say, a condition in which'the viscose remains plastic butactive in so far that evanescent cellulose formed by the decompositionprocess is present and combining or polymerizing, its duration being theshorter and its distribution throughout the filaments being thelesshomogeneous the greater is the hydrion concentra tion of thecoagulating acid; for example, in-a solution of hydrion concentrationequal to that ofa 0.5% solution of sulphuric acid the active plasticstate exists for distinctly less than 30' seconds, with a filament ofabout 1 denier, and most probably less than 10 seconds. 7 Ina solutionof 7 percent sulphuric acid the existence of the active plastic state isterminated in distinctly less than 3. seconds and probably less than 1.second, and,,superficially, considerably less than 1 second and betweenthese concentrations one. I has suflicient time to complete thestretching Process." I

In order that the .stretchingprocess may be completed within the.duration of existence of the active plastic state, as soon as thefilaments have sufficient solidity to permit of contact with asolidsurface I begin to apply tension which continues with increasing:stressso that the threads are extended at least 25% or even 100% or.more during the time the-viscose is'being decomposed, that is to say,during the existence of theactive plastic state. The time of applic'ation of tension is suchthat decompositionof the viscose into-celluloseis practically completed while the threadsarelbeing subjected totension. In practice the threads may remain under tension for a longertime than theaduration of existence ofthe active plastic state, butthe'actual extension of the threads only' proceeds while the viscose isin the plastic state.

According to a. further modification I use as coagulants-in a first bathany of the coagulants already referred to, but immediately or very soonafter their formation I pass the threads into a bathbf water, the secondbath, to which have been added such substancesas, while'permittingor'even assisting theswelling of the formed threads possibly by virtueof the presence of some active xanthogenate groupings, will not carrythe swelling process far enough to cause dissolution of the threads orwill prevent such dissolution; for example, neutral salts with additionof one or more orgamc'substances such a jet with many orifices, say a150 hole jet is used.

Permissible variants and details unnecessary to describe at lengthinclude the employment of viscose made in a particular way, and the useof mechanical devices of any form in the performance of the invention.

The figure of the accompanying drawing illustrates diagrammaticallyapparatus preferred for performing the process.

In the drawing A denotes a spinning bath into which viscose is deliveredthrough a jet. B denotes a pulley over which the filaments formed in thebath A are led from the bath. In the particular apparatus illustrated,the pulley B, assumed to have a circumference of 38.6 centimeters,rotates at the speed of twenty revolutions in seventy-two seconds. Fromthe pulley B the filaments are led to the pulley C rotating at the samespeed as the pulley 13. From the pulley C the filaments pass to thepulley D, of the same circumference as the pulley IB and performingtwenty revolutions in fifty-four seconds. The pulley D dips into thebath E, i.e., the second bath. From the pulley D the filaments submergedin the bath E pass to the pulley F rotating at the same speed as thepulley D. From the pulley F the filaments pass to the pulley G, thenceto the pulley H and thence to the spool J, which dips into an acidbathK.

In the particular apparatus illustrated, the

spool J, having a circumference of 29.8 centimeters, performs sixtyrevolutions in sixty-six seconds.

I claim:

1.The improvement in the manufacture of artificial filaments fromviscose, consisting in coagulating the viscose in the form of filamentsin acids of a hydrion concentration less than that of 7% H2804, causingthe viscose to enter an evanescent active plastic state, then passingthe filaments into a bath of water to which have been added substanceswhich permit the swelling of the formed filaments by the action of thewater, without bringing about dissolution of the filaments, andstretching the filaments before complete decomposition of the viscose,substantially as described.

2. The improvement in the manufacture of artificial filaments fromviscose, consisting in eifecting coagulation of the viscose, in the formof filaments, in acids of hydrion concentration less than that of 7%H2504, whereby the filaments are caused to enter an evanescent activeplastic state, and gradually applying tension to the filaments to effectextension of the filaments commencing with solidification of thefilaments and continuing While the filaments are in said evanescentactive plastic state, whereby the filaments are extended at least 25%before complete decomposition of the viscose.

W. HARRISON.

